A solid oxide fuel cell (hereinafter, referred to as SOFC) is known as a versatile highly efficient fuel cell. Since, in the SOFC, the operation temperature is set high in order to enhance the ion conductivity, the SOFC can use the air discharged from a compressor of a gas turbine as an air (oxidant) to be supplied to an air electrode (cathode). In addition, an unused high-temperature fuel and waste heat exhausted from the SOFC can be used as fuel and an oxidant in the combustor of the gas turbine. Further, other than the SOFC, a molten carbonate fuel cell is known as a fuel cell having a high operation temperature, and, similarly to the SOFC, the use of waste heat thereof in cooperation with a gas turbine has been examined.
Therefore, for example, as disclosed in Patent Literatures 1 to 3, various power generation systems constituted by combinations of an SOFC, a gas turbine, and a steam turbine have been proposed as a power generation system capable of achieving highly efficient power generation. A SOFC power generation facility disclosed in Patent Literature 1 is provided with a heating side of a cathode heat exchanger, a cooler, and a recycle blower in a cathode recycle line, cools a cathode gas having passed through the fuel cell with the cathode heat exchanger and the cooler, and recirculates the gas in the cathode gas line. Further, a hybrid power generation system disclosed in Patent Literature 2 is provided with an exhausted fuel recirculation blower that supplies a part of the fuel to a hydrogen fuel to be supplied to a fuel cell, and a heat exchanger for fuel that heats the fuel by a recirculating fuel. In addition, the SOFC hybrid power generation plant system disclosed in Patent Literature 3 is provided with a heat exchanger for heating fuel that heats fuel in a fuel supply line by an exhausted fuel in the exhaust fuel line.